--- /dev/null
+## Copyright (C) 2003 David Bateman
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 3 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{code} =} encode (@var{msg},@var{n},@var{k})
+## @deftypefnx {Function File} {@var{code} =} encode (@var{msg},@var{n},@var{k},@var{typ})
+## @deftypefnx {Function File} {@var{code} =} encode (@var{msg},@var{n},@var{k},@var{typ},@var{opt})
+## @deftypefnx {Function File} {[@var{code}, @var{added}] =} encode (@var{...})
+##
+## Top level block encoder. This function makes use of the lower level
+## functions such as @dfn{cyclpoly}, @dfn{cyclgen}, @dfn{hammgen}, and
+## @dfn{bchenco}. The message to code is pass in @var{msg}, the
+## codeword length is @var{n} and the message length is @var{k}. This
+## function is used to encode messages using either:
+##
+## @table @asis
+## @item A [n,k] linear block code defined by a generator matrix
+## @item A [n,k] cyclic code defined by a generator polynomial
+## @item A [n,k] Hamming code defined by a primitive polynomial
+## @item A [n,k] BCH code code defined by a generator polynomial
+## @end table
+##
+## The type of coding to use is defined by the variable @var{typ}. This
+## variable is a string taking one of the values
+##
+## @table @code
+## @item 'linear' or 'linear/binary'
+## A linear block code is assumed with the coded message @var{code} being in
+## a binary format. In this case the argument @var{opt} is the generator
+## matrix, and is required.
+## @item 'cyclic' or 'cyclic/binary'
+## A cyclic code is assumed with the coded message @var{code} being in a
+## binary format. The generator polynomial to use can be defined in @var{opt}.
+## The default generator polynomial to use will be
+## @dfn{cyclpoly(@var{n},@var{k})}
+## @item 'hamming' or 'hamming/binary'
+## A Hamming code is assumed with the coded message @var{code} being in a
+## binary format. In this case @var{n} must be of an integer of the form
+## @code{2^@var{m}-1}, where @var{m} is an integer. In addition @var{k}
+## must be @code{@var{n}-@var{m}}. The primitive polynomial to use can
+## be defined in @var{opt}. The default primitive polynomial to use is
+## the same as defined by @dfn{hammgen}.
+## @item 'bch' or 'bch/binary'
+## A BCH code is assumed with the coded message @var{code} being in a binary
+## format. The generator polynomial to use can be defined in @var{opt}.
+## The default generator polynomial to use will be
+## @dfn{bchpoly(@var{n},@var{k})}
+## @end table
+##
+## In addition the argument 'binary' above can be replaced with 'decimal',
+## in which case the message is assumed to be a decimal vector, with each
+## value representing a symbol to be coded. The binary format can be in two
+## forms
+##
+## @table @code
+## @item An @var{x}-by-@var{k} matrix
+## Each row of this matrix represents a symbol to be coded
+## @item A vector
+## The symbols are created from groups of @var{k} elements of this vector.
+## If the vector length is not divisble by @var{k}, then zeros are added
+## and the number of zeros added is returned in @var{added}.
+## @end table
+##
+## It should be noted that all internal calculations are performed in the
+## binary format. Therefore for large values of @var{n}, it is preferable
+## to use the binary format to pass the messages to avoid possible rounding
+## errors. Additionally, if repeated calls to @dfn{encode} will be performed,
+## it is often faster to create a generator matrix externally with the
+## functions @dfn{hammgen} or @dfn{cyclgen}, rather than let @dfn{encode}
+## recalculate this matrix at each iteration. In this case @var{typ} should
+## be 'linear'. The exception to this case is BCH codes, whose encoder
+## is implemented directly from the polynomial and is significantly faster.
+##
+## @end deftypefn
+## @seealso{decode,cyclgen,cyclpoly,hammgen,bchenco,bchpoly}
+
+function [code, added] = encode(msg, n, k, typ, opt)
+
+ if ((nargin < 3) || (nargin > 5))
+ usage ("[code, added] = encode (msg, n, k [, typ [, opt]])");
+ endif
+
+ if (!isscalar(n) || (n != floor(n)) || (n < 3))
+ error ("encode: codeword length must be an integer greater than 3");
+ endif
+
+ if (!isscalar(k) || (k != floor(k)) || (k > n))
+ error ("encode: message length must be an integer less than codeword length");
+ endif
+
+ if (nargin > 3)
+ if (!ischar(typ))
+ error ("encode: type argument must be a string");
+ else
+ ## Why the hell did matlab decide on such an ugly way of passing 2 args!
+ if (strcmp(typ,"linear") || strcmp(typ,"linear/binary"))
+ coding = "linear";
+ msgtyp = "binary";
+ elseif (strcmp(typ,"linear/decimal"))
+ coding = "linear";
+ msgtyp = "decimal";
+ elseif (strcmp(typ,"cyclic") || strcmp(typ,"cyclic/binary"))
+ coding = "cyclic";
+ msgtyp = "binary";
+ elseif (strcmp(typ,"cyclic/decimal"))
+ coding = "cyclic";
+ msgtyp = "decimal";
+ elseif (strcmp(typ,"bch") || strcmp(typ,"bch/binary"))
+ coding = "bch";
+ msgtyp = "binary";
+ elseif (strcmp(typ,"bch/decimal"))
+ coding = "bch";
+ msgtyp = "decimal";
+ elseif (strcmp(typ,"hamming") || strcmp(typ,"hamming/binary"))
+ coding = "hamming";
+ msgtyp = "binary";
+ elseif (strcmp(typ,"hamming/decimal"))
+ coding = "hamming";
+ msgtyp = "decimal";
+ else
+ error ("encode: unrecognized coding and/or message type");
+ endif
+ endif
+ else
+ coding = "hamming";
+ msgtyp = "binary";
+ endif
+
+ added = 0;
+ if (strcmp(msgtyp,"binary"))
+ vecttyp = 0;
+ if ((max(msg(:)) > 1) || (min(msg(:)) < 0))
+ error ("encode: illegal value in message");
+ endif
+ [ncodewords, k2] = size(msg);
+ len = k2*ncodewords;
+ if (min(k2,ncodewords) == 1)
+ vecttyp = 1;
+ msg = vec2mat(msg,k);
+ ncodewords = size(msg,1);
+ elseif (k2 != k)
+ error ("encode: message matrix must be k columns wide");
+ endif
+ else
+ if (!isvector(msg))
+ error ("encode: decimally encoded message must be a vector");
+ endif
+ if ((max(msg) > 2^k-1) || (min(msg) < 0))
+ error ("encode: illegal value in message");
+ endif
+ ncodewords = length(msg);
+ msg = de2bi(msg(:),k);
+ endif
+
+ if (strcmp(coding,"bch"))
+ if (nargin > 4)
+ code = bchenco(msg,n,k,opt);
+ else
+ code = bchenco(msg,n,k);
+ endif
+ else
+ if (strcmp(coding,"linear"))
+ if (nargin > 4)
+ gen = opt;
+ if ((size(gen,1) != k) || (size(gen,2) != n))
+ error ("encode: generator matrix is in incorrect form");
+ endif
+ else
+ error ("encode: linear coding must supply the generator matrix");
+ endif
+ elseif (strcmp(coding,"cyclic"))
+ if (nargin > 4)
+ [par, gen] = cyclgen(n,opt);
+ else
+ [par, gen] = cyclgen(n,cyclpoly(n,k));
+ endif
+ else
+ m = log2(n + 1);
+ if ((m != floor(m)) || (m < 3) || (m > 16))
+ error ("encode: codeword length must be of the form '2^m-1' with integer m");
+ endif
+ if (k != (n-m))
+ error ("encode: illegal message length for hamming code");
+ endif
+ if (nargin > 4)
+ [par, gen] = hammgen(m, opt);
+ else
+ [par, gen] = hammgen(m);
+ endif
+ endif
+ code = mod(msg * gen, 2);
+ endif
+
+ if (strcmp(msgtyp,"binary") && (vecttyp == 1))
+ code = code';
+ code = code(:);
+ elseif (strcmp(msgtyp,"decimal"))
+ code = bi2de(code);
+ endif
+
+endfunction
git://git.creatis.insa-lyon.fr / CreaPhase.git / blobdiff